DDE and PCBs are environmental toxins that are nearly universally detectable in human tissues. They are known to have inter-generational reproductive toxicity in animals, which suggests that they act as endocrine disrupters. No studies have investigated the effects of prenatal exposure to background levels of these toxins in women, although studies in animals suggest that prenatal exposures at lower doses may have profound effects. This epidemiological study will investigate the inter-generational effects of exposure to DDT/DDE and the PCBs in a subset of a unique study population, the Child Health and Development Studies (CHDS), consisting of 312 mother-daughter pairs followed for more than 30 years since mothers' pregnancies in 1960-1963, a period of high exposure to DDE and PCBs. We will study the following markers of endocrine disruption: 1) Fecundability in women exposed prenatally. 2) Endocrine status (estrogens) in the early follicular phase of the menstrual cycle among women exposed prenatally. Significantly, fecundability is a sensitive and efficient indicator of reproductive toxicity. This study will investigate the following primary hypothesis: 1) Prenatal DDE and PCB exposure are associated with decreased fecundability in women. This study will also complete a pilot study to evaluate the hypothesis that prenatal DDE and PCB exposures at background levels are associated with levels of estrogen in menstruating women. In summary, the proposed study will provide the first inter-generational investigation of the relation of organochlorine exposure at background levels to reproductive performance and endocrine function. The study can be accomplished at low cost because it uses existing data.